1. Field of the Invention
The present invention relates to a terminal connection apparatus for bridging between terminals of neighboring electrical devices (e.g., contactors (relays), on/off devices).
2. Prior Art
According to a known arrangement, when a motor is normal/reverse-operated, or when one power source is connected to two loads in a switching manner, or when two power sources are connected to one load in a switching manner, two electromagnetic contactors (relays) or two similar on/off devices are provided so as to be physically adjacent to each other, and a terminal connection apparatus is used for bridging the terminals of these devices using terminal connection conductors. FIGS. 5A, 5B and 5C illustrate wiring diagrams of a three-pole electromagnetic contactor in various applications using such a terminal connection apparatus.
FIG. 5A shows the connection in which two electromagnetic contactors 1 are used to perform normal/reverse operation of a motor. Here, with regard to the power source side, the space between the two terminals 1, the space between the two terminals 3, and the space between the two terminals 5 are bridged by the terminal connection conductors 2, 3, and 4 in the order of phases (i.e., the same phases are bridged). With regard to the load side, the space between terminals 2 and 6, the space between the two terminals 4, and the space between terminals 6 and 2 are bridged by the terminal connection conductors 5, 6, and 7 in the order in which the phases are switched, i.e., to be bridged so that two of the three phases are interchanged. As is well known, a three-phase AC motor can provide normal/reverse rotation by switching two among three of the phases R, S, and T. Thus, treating the condition in which the electromagnetic. contactor 1 at the left of FIG. 5A is in the “ON” condition as normal rotation, then reverse rotation is provided when the right side is in the “ON” condition. Similar switching also can be provided when the power source side and the load side are switched directly.
FIG. 5B shows two electromagnetic contactors 1 used to switch two loads A and B, in which the power source side is bridged in the order of the phases. When the left side of FIG. 5B is turned ON, then the load A is supplied with power and, when the right side is turned ON, then the load B is supplied with power. FIG. 5C shows two electromagnetic contactors 1 used to switch two power sources A and B, in which the load side is bridged in the order of the phases. When the left side of FIG. 5C is turned ON, the power source A is supplied to the load and, when the right side is turned ON, the power source B is supplied to the load.
FIGS. 6A and 6B show an example in which a conventional terminal connection apparatus is used to provide a reversible type electromagnetic contactor for the normal/reverse operation of a motor, where FIG. 6A is a side view and FIG. 6B is a front view. Two electromagnetic contactors 1 are provided on an attachment base 8 so as to be adjacent to each other and are interlocked by a mechanical interlock apparatus 9 so that the two contactors are not turned ON at the same time. As shown, the space between the terminals at the power source side (upper side) is bridged by the terminal connection conductors 5 to 7 in the order of the switching of the phases, while the space between the terminals at the load side (lower side) is bridged by the terminal connection conductors 2 to 4 in the order of the phases.
FIGS. 7A, 7B and 7C are respectively a side view, a front view and a lower face view of a terminal connection conductor, such as the terminal connection conductor 2 in FIGS. 6A and 6B, in the exemplary conventional terminal connection apparatus. The terminal connection conductor 2 consists of a U-shaped conductor punched out of a plate material, both ends of which are bent at a right angle to provide a terminal section 2a. The space between the terminal sections 2a is covered by an insulation material 10. The insulation material 10 is applied, for example, with a polyethylene resin immersion coating or a powder insulation coating.
FIGS. 8A, 8B and 8C are respectively a side view, a front view and a lower face view of another example of the terminal connection conductor 2 in FIGS. 6A and 6B. Here, terminal connection conductor 2 has the same structure as that of FIGS. 7A, 7B and 7C, but the former is different from the latter in that the insulation material 10 is formed by a tube that contracts when subjected to heat. In FIGS. 6A and 6B, for the purpose of saving space, the terminal connection conductor 3 is provided to have a Ω-like shape and the terminal connection conductor 6 is provided to have a strip-like shape, and they are connected to the terminal connection conductors 2 and 4 and the terminal connection conductors 5 and 7 so as to be perpendicular thereto.
Spanish Patent Publication No. ES2081243 discloses a different conventional technique in a terminal connection apparatus for bridging the terminals of two electrical devices provided to be adjacent to each other. This apparatus is designed so that an electrical insulation element having a groove for guiding an electric wire is provided, and an electric wire is inserted in the groove for bridging between the terminals.
If the terminal connection conductor of FIGS. 7A, 7B and 7C is coated for insulation by an immersion coating or a powder insulation coating, the insulation coating can be applied, as shown, up to the root of the terminal section. However, a problem arises in that the insulation coating material needs to be dried for a long time, so it has poor workability. In contrast, in the terminal connection conductor of FIGS. 8A, 8B and 8C using a thermal contraction tube, when compared to the conventional example of FIGS. 7A, 7B and 7C, the insulation coating has superior workability. such a thermal contraction tube tends to develop wrinkles during contraction, and the corner section where the conductor is bent in particular tends to have a complicated shape due to the wrinkles. In view of this, when a thermal contraction tube is used, conventional techniques have prevented such a conductor bend section from being maximally insulation-coated, so that the insulation coating is provided only in the middle part of the U-shaped section (see FIGS. 8A, 8B and 8C). Thus, the conductor is exposed in a wider area, which runs the risk of a short-circuit when this exposed part comes in contact with a conductive foreign material (e.g., scraps of electric wire), or of causing an electric shock if contacted by a finger, for example. The terminal connection apparatus for reversible operation of FIGS. 6A and 6B also has a problem of incorrect wiring because six terminal connection conductors must be connected separately.
On the other hand, with the apparatus according to Spanish Patent Publication No. ES2081243 in which an electric wire is inserted to the groove of an electrical insulation element, exposed electric wiring is contained in a narrower space, which reduces the risk of electric shocks. This apparatus also has an advantage that the wiring can be arranged with more precision because terminals can be connected after all electric wires have been retained by electrical insulation elements. However, grooves in which electric wires are inserted require different routing patterns in accordance with the wiring type (e.g., order of phase, phase switching), thus increasing the complexity of the layout process. A deeper groove for providing an enhanced insulation also tends to cause deformation of the resin-formed electrical insulation element, which may cause a problem in inserting the wiring into the groove. Such a groove also creates a risk that the insulation of an electrical insulation element may deteriorate from dust or the like, because the groove in the electrical insulation element is in an “open” condition before an electrical wire is inserted.
The present invention is intended to solve these problems. It is an objective of the invention to improve the insulation of the terminal connection conductor, to prevent incorrect wiring, and to simplify the wiring work and the management of components.